EVENTS

A sky full of moons

A single crescent moon is a familiar sight in Earth’s sky, but with Saturn’s many moons, you can see three or even more.

The three moons shown here — Titan (3,200 miles or 5,150 kilometers across), Mimas (246 miles or 396 kilometers across), and Rhea (949 miles or 1,527 kilometers across) — show marked contrasts.

Titan, the largest moon in this image, appears fuzzy because we only see its cloud layers. And because Titan’s atmosphere refracts light around the moon, its crescent “wraps” just a little further around the moon than it would on an airless body. Rhea (upper left) appears rough because its icy surface is heavily cratered. And a close inspection of Mimas (center bottom), though difficult to see at this scale, shows surface irregularities due to its own violent history.

I like how Titan has the cartoon-crescent-moon thing going on where the arc is more than 180 degrees. It isn’t actually possible to get that usually, because the sun only illuminates half the sphere at a time. But apparently an atmosphere can refract the light further around. That’s 200 degrees at least.

I showed this to my friends, explained all about Saturn’s moons in great detail and with much enthusiasm. They immediately started an argument amongst themselves as to whether the image was missing one wolf or nine. Barbarians.